Some algorithms of recreational mathematics that I did as exercises in my first (and only) semester studying Computer Science.

gistfile1.cpp

int getFactorialOf(unsigned number) {

	if (number == 0) {
	
		return 1;
	
	}

	unsigned int factorial, i;

	for (factorial = i = 1; i <= number; factorial *= i, i++);

	return factorial;

}

gistfile2.py

def isNarcissistic(number):

    # Determines the number of digits:
    digits = 0
    for (dividend = number; dividend > 0; dividend //= 10):
        digits += 1

    # Calculates the sum of the squared digits:
    digitsSum = 0
    for (dividend = number; dividend > 0; dividend //= 10):
        digitsSum += (dividend % 10) ** digits

    # Returns the answer:
    if (digitsSum == number):
        return true

    return false

gistfile3.cpp

bool isHappy(unsigned int number) {

	unsigned int sum;

	do {

		sum = 0;
		for (; number > 0; sum += (number % 10) * (number % 10), number /= 10);
		if (sum < 10) break;
		number = sum;
		
	} while (true);

	if (sum == 1) return true;

	return false;

}

gistfile4.cpp

bool isRepunit(number) {

	while (number > 0) {

		if (number % 10 != 1) return false;
		number /= 10;

	}

	return true;

}

gistfile5.cpp

bool isPrime(long int number) {

	if (number <= 1) return false;
    
	if (number == 2) return true;

	for (unsigned int i = 2; i < (number / 2) + 1; ++i) {

		if (number % i == 0) return false;

	}

	return true;

}

gistfile6.cpp

bool isAutomorphic(number) {

    unsigned int digits = 0, divisor = 1, squareNumber = number * number;

	// Calculate the number of digits:
	for (unsigned int i = number; i > 0; i /= 10, ++digits);

	// Calculate the divisor to use:
	for (int i = 1; i <= digits; divisor *= 10, i++);

	if ((squareNumber % divisor) == number) return true;

	return false;

}

gistfile7.cpp

bool isPalindromic(unsigned int number) {

	int reversed = 0;

	// Reverse the number:
	for (unsigned int i = number; i > 0; reversed = (10 * reversed) + (i % 10), i /= 10);

	if (reversed == number) return true;

	return false;

}

gistfile8.cpp

bool isPerfect(unsigned int number) {

	unsigned int divisorsSum = 1;

	for (divisor = 2; divisor <= (number / 2) + 1; ++divisor) {

		if (number % divisor == 0) {

			divisorsSum += divisor;

		}

	}

    if (number == divisorsSum) {

		return true;

	}

	return false;

}

gistfile9.cpp

# Change the base of a decimal base integer
unsigned int(unsigned int number, unsigned short int newBase) {

	unsigned int baseChanged = 0, exponent = 1;

	for (unsigned int quotient = number; quotient > 0; quotient /= base) {

		baseChanged += exponent * (quotient % base);
		exponent = (10 * exponent);

	}

	return baseChanged;

}